Natural Hazards and Disasters 4 - E-thaksalawa · Natural Hazards and Disasters Fig. 4.1. - Several...

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Natural Hazards and Disasters

Fig. 4.1. - Several disasters

Natural phenomena that may cause damage to community or property are hazards. A hazard is a continuous process. If such

incidents affect either the community or property, they become a disaster.

Fig. 4.2 - Hazard Fig. 4.3 - Disaster

4 At present, we always hear about different natural disasters. Human lives, property, the public facilities and natural environment are threatened due to these disasters.

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Activities1. Name five natural hazards you have heard of.2. State five damages that a natural disaster could cause.3. Prepare a fact file using pictures about natural disasters.

Natural Disasters in Sri Lanka A natural disaster is a destructive force that may occur within a short period of time. At present, Most of the hazards found in Sri Lanka are increasingly turning into disasters due to unfavourable human activities. Several hazards such as droughts, floods, earth slips, cyclones, lightning, tsunamis and earth quakes are some examples for such instances.

The objective of this chapter is to study both natural hazards and disasters and about the natural disasters that occur in Sri Lanka.

Earth slips is a hazard that occurs in hilly areas. It becomes a disaster according to its impact on people and property. An earth slip that occurs in an uninhabited island is only a natural hazard as it does not damage people or property. However, if it occurs in a densely populated region, it becomes a disaster.

DroughtThe dry condition that prevails for a long period in a certain

area, as a result of the delay in the rainfall due for a particular period.

Drought is a hazard that can exist in a region at any period. However the attention focused on drought is less. It is because, a drought is a silent destructive force that begins without our knowledge and develops gradually creating a crisis in the whole human society. Map 4.1 shows several districts of Sri Lanka where droughts occur.


Impacts on man.

Reasons for droughts ² Decrease of rainfall over

a longer period. ² Setting fire to forests. ² Dry wind currents. ² Increase of global

warming. ² Removal of vegetation

cover.

Map 4.1 - Several districts in Sri Lanka where droughts occur

Damages caused by drought

The harmful impacts of the drought can be discussed under two fields, as impacts on man and impacts on the environment.

Activities

² Scarcity of water ² Destruction of crop harvest ² Scarcity of food ² Spread of epidemics. ² Damage to animals


Impacts on the environment

Activities1. Mark and shade the districts on a map of Sri Lanka where

droughts occur.

2. Write two reasons for droughts.

3. Present three factors as to how a drought affects human activities.

4. Prepare a report either observing or collecting information on the changes occur in the environment during a drought.

Flood When a large mass of water is collected in rivers, canals streams, reservoirs and other natural waterways in a short period of time, they begin to overflow. At present, flooding of rainwater even in a light shower is a common feature in urban areas where

Map 4.2 - Several districts that are subjected to disaster of flood in Sri Lanka.

² Increase in environmental temperature.

² Decrease in ground water level.

² Occurance of bush fires. ² Destruction of forests. ² Destruction of bio resources. ² Infertility of soil. ² Damage to scenic beauty.

Flood When a large mass of water is collected in rivers, canals streams, reservoirs and other natural waterways in a short period of time, they begin to overflow. At present, flooding of rainwater even in a light shower is a common feature in urban areas where


rivers and other waterways are not found. Map 4.2 shows several districts where floods occur in Sri Lanka. Yet, with the increase in the intensity of rainfall, floods may occur in all districts of Sri Lanka.Reasons for flood

² Incessant heavy rains ² Clearing of forests in hilly areas ² Reclamation of lowlands ² Sand mining in river valleys

Activities 1. i. Mark and name five river valleys where floods occur

on an outline map of Sri Lanka. ii. Shade five districts where floods occur on the same map.2. In which climatic zone do floods occur frequently?3. What are the districts in the dry zone where floods may occur?4. Draw a picture to show a flooded area.

Fig. 4.4 - Damages due to flood


Earth slips

Damages from Earth slips

² Loss of lives and property. ² Destruction of cultivated

lands. ² Destruction of the

environment. ² Water bodies become shallow

and canals are blocked. ² Destruction of infrastructure

facilities. ² Impairment of normal life.

Map 4.3 - Several districts of Sri Lanka where earth slips occur.

Sliding of a large portion of the earth located at a higher elevation downwards along a slope with rock boulders, gravel and soil lumps is

called an earth slip.

At present, earth slip is a common disaster in Sri Lanka. Though it is a natural process, human activities influence it to a great extent. Reasons for the earth slips can be divided into two categories.

Natural Causes Human Activities ² Incessant rain ² Lands with steep slope. ² Existence of weathered

rock layers. ² Earth quakes.

² Setting fire to the forests in mountainous areas.

² Improper use of land in mountainous areas.

² Insufficient research before doing constructions.

² Blocking of natural water ways.. ² Storing of water in highlands.

Map 4.3 shows the districts of Sri Lanka where earth slips occur frequently.


Map 4.4 - Several districts of Sri Lanka subjected to the influence

of cyclones

Activities1. Briefly explain what a landslide is.2. Mark and shade five districts where landslides occur frequently in

an outline map of Sri Lanka.3. Select the reasons for landslides from the list given below Wind,

heavy rains, high temperature, reclamation of lowlands, steep slopes, cultivation in hilly areas, flat lands, storing water in high lands, blocking river mouths, earth quakes.

4. Create a poster depicting the disasters that could occur during an earth slip.

5. Suggest three actions that can be taken to prevent earth slips.

The hard blowing wind while spinning fast in a swirl is known

as a cyclone or a storm.

Cyclones (Storms)

High temperatures in a tropical zone and development of low pressure centers influence the origin of cyclones.

Sri Lanka is a country located in the tropical zone. Due to the influence of the low pressure centers that originate in the Bay of Bengal, Sri Lanka is affected by cyclones frequently.

The cyclonic winds enter the island from the Eastern and North East coasts and exit from the


North Western coast. As a result the Northern and Eastern regions of Sri Lanka are highly affected by cyclones. Identify the regions affected by the cyclones by observing the Map of Sri Lanka.

Activities1. What is a cyclone?2. On a map of Sri Lanka mark and shade the districts of Sri Lanka

that get affected by the cyclones.3. Prepare a list of damages caused by cyclones.4. Present suggestions to minimize these damages.

Thunderbolts (Lightning)Discharge of an electric current between two opposite charges

due to the electric phenomenon that occur in a cloud is known as a thunderbolt.

Accordingly, discharge of an electric current may occur in a cloud itself, between two clouds or from a cloud to the earth. These electric currents can cause huge damages. Although, lightning may occur any time of the year, in Sri Lanka, it often occurs during the months of March- April and October- November when the convectional process is active.


Damages of Thunderbolts/ lightning ² Loss of lives and property. ² Breaking down of electric cable systems. ² Destruction of houses. ² Breaking down of communication networks.

Prevention of Thunderbolt accidents ² Keep away from open places when there are thunder showers. ² Keep away from tall trees. ² Avoid travelling during such occasions. ² Disconnect all domestic electric circuits. ² Do not use telephones. ² Do not construct buildings under high tension electric lines. ² In house constructions, installing of electric circuits should

safely be done by a skilled technician.

Activities1. Prepare an instructional hand out to make people of aware of

the methods that could be followed to prevent or minimize the accidents of lightning.


TsunamiThe waves that travel fast towards the coast due to the occurrance

of earth quakes, earth slips or volcanic eruptions in the sea bed are called tsunami.

Tsunami is a word derived from Japanese language. “Tsu” meaning “harbour” and “nami” meaning “waves". Tsunamis are also known as very tall waves that move towards the coast.

Since Sri Lanka is an island, all the lands associated with the coastal area around it are open to this hazard. Though it is not a common disaster like others, the impact is enormous. The catastrophic tsunami that affected Sri Lanka on 26th of December, 2004 resulted massive destruction of lives and property.

Causes for Tsunami ² Earth Quakes, ² Earth Slips, ² Volcanic eruptions occur in the sea bed ² Falling of meteors into oceans.

² Loss of lives

² Mental stress caused in people

² Pollution of water and land

² Collapse of fisheries activities, coir and tourist industries.

² Displacement of people

² Destruction of plants and animals

² Destruction of infrastructure facilities like water supplies, electricity and roads

² Destruction of houses, buildings, vehicles, business premises

² Destruction of coastal lagoons, river mouths, mangroves, marshy lands and sea weeds

Dam

ages

from

Tsu

nam

i


How to escape from a Tsunami ² Be alert about Tsunami warnings. ² Do not stay close to the sea to look at the receding of sea during a

tsunami condition. ² Go to a safe higher place as soon as possible

Activities1. Define what a tsunami is.2. Write three causes for tsunami.3. When did tsunami conditions affect Sri Lanka?4. Mark and name the regions of Sri Lanka that were affected by the

tsunami disaster on an outline map of Sri Lanka.Earth quakes

A sudden tremor that occurs in the earth due to the high temperature in the interior of the earth and changes in pressure is

known as earth quake. Though the hazard of the earth quake is present in every part of Sri Lanka, it has not converted into a condition of disaster yet, but, earth quakes occurring in nearby regions may also affect Sri Lanka.

Reasons for Earth quakes ² High temperature in the interior of the earth and changes in

pressure ² Breaking down of the equilibrium of the earth due to the

construction of reservoirs and large scale constructions ² Nuclear explosions ² Volcanic eruptions

Damages from Earth quakes ² Loss of lives and property ² Displacement of people ² Slowing down of day today activities ² Destruction of cultivated lands ² Destruction of vegetation and animals


Activity1. Complete the following table with damages from earth quakes.

Damages to the people Damages to the environment.

Facing a disaster Man cannot prevent natural disasters completely. But their effect can be minimized. Disaster management is important for it. The basic steps for disaster management are preparedness, response and recovery. Following examples show how we should respond to natural disasters shown above according to the disaster management cycle.

² Collect victims to safety places.

² Attempt to protect lives than property.

²Face the disaster strongly. ²Provide medical assistance

and treatments to the victims.

² Provide food and beverages to the refugees.

² Move away from the buildings where accidents could occur.

² Avoid consuming polluted and contaminated food.

² Identify the hazardous zones and moving away from them.

² Make people aware of disaster, place of disaster, and period when a disaster could occur.

² Protect the forest cover. ² Protect the catchment areas. ² Fix lightning conductors to the

buildings. ² Do not construct buildings under

high tension electric lines. ² Build houses that resist disasters. ² Be alert about tsunami condition

(warning) when an earth quake occurred in an adjoining zone.

Preparedness Response (During Disaster)


² Identify problems. ² Establish emergency disaster

centers. ² Introduce disaster kits.( life

saving kits.)

Recovery ² Provide relief to the victims. ² Conduct health programmes. ² Plan the activities to restore the

mental health of the victims.

occur in your region.4. Complete the following table.

Natural Disaster Reasons Methods of minimizing the damage

Flood 01.02.

Droughts 01.02.

Cyclones 01.02.

Earth Slips 01.02.

Assignment1. Name two natural disasters that occur frequently in Sri Lanka.2. Prepare a fact file including pictures of areas that have affected by

natural disasters (collected from newspapers, magazines etc.)3. Find and present the causes for these disasters.4. Get into groups and prepare a hand-out including the steps that

could be used to aid the victims.

Activities1. Name five natural hazards2. Explain the difference between natural hazards and disasters.3. Complete the following table with reference to the disasters that

Long-term or short term changes that happen in the general climatic pattern is known as climatic changes.

Global Climatic Changes


It is seen that though it took a longer period for changes in the climate in the past, they occur in a short period of time at present. Drought, harsh cold seasons, floods, cyclones etc can be identified as the results of these changes. Such climatic changes that take place globally have influenced Sri Lanka too.Reasons for climatic changes.

² Excessive burning of fossil fuel ² Destruction of forests ² Warming of the atmosphere ² Burning of agro and industrial waste ² Volcanic eruptions

How climatic changes affect Sri Lanka.1. Destruction of coastal eco systems due to the rise of sea level. ² Inundation of coastal lands. ² Pollution of drinking water. ² Increase in coastal erosion. ² Breaking down of fishing industry and destruction of coastal

industries.2. Destructions caused by heavy rains ² Floods and earth slips ² Loss of lives and property. ² Destruction of infrastructure facilities. ² Reduction of agro harvest.

3. Destructions due to the increase of atmospheric temperature. ² Occurrance of droughts. ² Scarcity of water. ² Decrease in harvest. ² Changes in agricultural patterns and types of crops. ² Increase the spreading of diseases, mostly that could not be

diagnosed easily ² Spread of skin, eye, and respiratory diseases. ² Occurrance of mental stress.

4. Emergence of crisis connected to the production and use of energy sources.

² Increase in the use of air condition equipment and fans due to the increase in temperature.


² Slowing down of the generation of hydro electricity. ² Increase of the demand for electricity and thermal power energy.

5. Actions Taken to Minimize the Climatic Changes. ² Minimize the emission of unfavourable gases like Carbon

Dioxide in the fields of industry, agriculture and transport. ² Minimize deforestation. ² Establish Forest Reserves. ² Intensify the use of bio gases with less effect on the environment. ² Enact limits to the emission of Green House Gases that increases

the global warming. ² Solid waste management. ² Pass laws to stop unauthorized constructions. ² Make people aware. ² Work collaboratively with the other countries in the world.

Activities.

1. What are the reasons for the global climatic changes?

2. State three environmental damages that occur due to the increase in global warming.

Assignments1. Describe briefly how you could contribute to minimize the climatic

changes.2. i. Create a poster including protective steps to make aware the

victims of such disasters.3. Present a report, finding the reasons for the increase of accidents of

thunderbolt using newspapers. 4. Propose three steps you use to get away if you happen to face such

a disaster 5. i. If a natural disaster has occurred in your area or area around

your school. visit that place with your teacher or an adult and observe the disaster.

ii. Record the damage of that disaster. iii. Collect the reasons for that disaster by inquiring. iv. Present a report to the class including all information. v. Discuss and present the steps that could be used to prevent or minimize those damages.


Glossary ² Natural Hazards - iajdNdúl Wmøj - C¯ØøP AÈÄPÒ

² Disasters - wdmod - AÚºzu[PÒ

² Drought - kshÕh - Áµm]

² Wind - iq<x m%jdy - PõØÖUPÒ

² Global Warming - f.da,Sh WKqiqu - §÷PõÍ öÁ¨£®

² Bush Fire - ,eõ .sks - Põmkz w

² Flood - .xj;=r - öÁÒÍ¨ö£¸US

² Earth Slips/ Landslides - kdhhEï - {»a\›Ä

² Rocks - mdIdK - £õøÓPÒ

² Cyclones - iq<s iq<x - `ÓõÁÎ

² Thunderbolt - wl=Kq ier - ªßÚÀ uõUP®

/Lightning ² Electric phenomenon - úoHq;a l%shdldß;ajh - C»zvµÛ¯À ö\¯Ø£õk

² Convectional Process - ixjyk l%shdj,sh - ÷©ØPõÄøPa ö\¯ß•øÓ

² Earth Quake - N+ñlïmdj - {»|kUP®

² Volcanic Eruption - .sksl÷ msmsÍu - G›©ø» PUSøP

² Equilibrium of - mDÓúsiu;=,s;;dj - ¦Â°ß \©{ø» the earth ² Nuclear Explosions - kHIAál msmsrùï - Aq öÁi¨¦

² Disaster Management - wdmÞ l<ukdlrKh - AÚºzu •Põø©zxÁ®

² Catchment Area - c, fmdaIl m%foaY- - }÷µ¢x¨¤µ÷u\[PÒ

² Lightning Conductors - wl=Kq ikakdhl - ªßÚÀ uõ[Q

² Hazardous Zones - wjÞkï l,dm - Ga\›UøP Á»¯[PÒ

² Emergency Disaster - yÈis wdmÞ uOHia:dk - AÁ\µ Â£zx ©zv ̄

Centers {ø»¯[PÒ

² Disaster Kits - wdmÞ lÜg, - Â£zx öuõhº£õÚ

P¸Âz öuõSvPÒ

² Global Climatic - f.da,Sh foaY.=‚l - E»PU Põ»{ø»

Changes -- fjkiaùu - ©õØÓ[PÒ

² Burning of Fuel - bkaOk oykh - G›ö£õ¸Ò £õÁøÚ

² Sea Erosion - fjr< Ldokh - Pøµ÷¯õµ A›¨¦

² Deforestation - jk yrKh -PõhÈ¨¦

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